In the burning of combustible material, such as in the incineration of hazardous waste, a problem often arises where the material is not completely combusted. This situation typically occurs due to the highly variable nature of the combustible material supplied for combustion. When material having a high fuel value per unit volume is introduced into a combustion zone for combustion, the oxygen supplied to the combustion zone may not be sufficient to completely combust the material. In addition, the combustion reaction will not be complete if the combustibles, such as waste, are not well-mixed with the oxygen provided to the combustion zone or if cold zones are present in the combustion zone. This results in the generation of products of incomplete combustion (PICs) which not only burden downstream cleaning steps, but also could comprise toxic or otherwise hazardous compounds which may be released to the atmosphere, thus presenting a potential health risk to the operators and to the local population.
Those skilled in this art have addressed this problem by injecting into the combustion zone additional oxygen when it appears that PICs are being generated in excessive amounts. The oxygen may be injected into the combustion zone in the form of air, oxygen-enriched air or technically pure oxygen. The higher the oxygen concentration of the oxidant injected into the combustion zone to deal with the PICs problems, the less is the quantity of unproductive nitrogen which is passed into the combustion which would burden the efficiency of the system and thus a higher oxygen concentration oxidant is preferred. Unfortunately, the higher is the oxygen concentration of the oxidant, the greater is the tendency for the subsequent combustion to form nitrogen oxides (NO.sub.x) which are themselves undesirable pollutants resulting from combustion processes. Thus, in attempting to reduce or eliminate one environmental pollutant (PICs) from a combustion reaction, there often results the generation of another environmental pollutant (NO.sub.x).
It is thus desirable to have a combustion method which can enable one to carry out a combustion reaction without the generation of excessive amounts of either PICs or NO.sub.x.
Accordingly it is an object of this invention to provide a combustion method whereby the generation of products of incomplete combustion is controlled without generating excessive amounts of nitrogen oxides.